Decomposition of Fast and Slow Cloud Responses to Quadrupled CO2 Forcing in BCC-AGCM2.0 over East Asia

• Published in: Advances in atmospheric sciences 2022-12, Vol.39 (12), p.2188-2202
• Main Authors: Zhou, Xixun, Xie, Bing, Zhang, Hua, He, Jingyi, Chen, Qi
• Format: Article
• Language: English
• Subjects: Aerosols; Atmospheric circulation; Atmospheric Sciences; Atmospheric temperature; Carbon dioxide; Carbon dioxide concentration; Cloud cover; clouds; Cooling effects; Decomposition; Earth and Environmental Science; Earth Sciences; General circulation models; Geophysics/Geodesy; Low clouds; Meteorology; Original Paper; precipitation; radiation; their interactions; Water circulation; Water vapor; Water vapour
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/s00376-022-1441-7

In this study, the decomposed fast and slow responses of clouds to an abruptly quadrupled CO 2 concentration (approximately 1139 ppmv) in East Asia (EA) are obtained quantitatively by using a general circulation model, BCC–AGCM2.0. Our results show that in the total response, the total cloud cover (TCC), low cloud cover (LCC), and high cloud cover (HCC) all increased north of 40°N and decreased south of 40°N except in the Tibetan Plateau (TP). The mean changes of the TCC, LCC, and HCC in EA were −0.74%, 0.38%, and −0.38% in the total response, respectively; 1.05%, −0.03%, and 1.63% in the fast response, respectively; and −1.79%, 0.41%, and −2.01% in the slow response, respectively. By comparison, we found that changes in cloud cover were dominated by the slow response in most areas in EA due to the changes in atmospheric temperature, circulation, and water vapor supply together. Overall, the changes in the cloud forcing over EA related to the fast and slow responses were opposite to each other, and the final cloud forcing was dominated by the slow response. The mean net cloud forcing (NCF) in the total response over EA was −1.80 W m −2 , indicating a cooling effect which partially offset the warming effect caused by the quadrupled CO 2 . The total responses of NCF in the TP, south China (SC), and northeast China (NE) were −6.74 W m −2 , 6.11 W m −2 , and −7.49 W m −2 , respectively. Thus, the local effects of offsetting or amplifying warming were particularly obvious.